Aiming for THE COASTAL ZONE (The narrow contact zone between land and sea.) Weathering 1. There are 2 main types of Weathering Freeze Thaw Weathering Occurs when temp hovers around 0C 1. Water seeps into rock cracks. 2. The water expands when it freezes putting rock under pressure. Upon thawing the pressure is released. 3. Process repeats eventually causing rock to break. 1. Mechanical: breakdown is physical break up of rock. At the coast this is by freeze-thaw Terminology
Weathering: the breakup or decay of rocks in their original place at, or close to, the earths surface 2. 3. Carbonation Weathering Occurs in warm, wet conditions. Water in the air mixes with CO2 to produce weak carbonic acid . 2. Chemical: the chemistry of the rock is altered. At the coast this is mainly by carbonation, however salt spray can play a part. H2O + CO2
H2CO3 Alkaline rocks such as chalk and limestone are dissolved by the acid. Terminology Mass Movement a)Slides Drier material moves horizontally along bedding slip plane of rock. Mass Movement The downhill movement of material under the influence of gravity Types of Mass Movement b) Slumps Saturated material moves in a circular rotation as it is pulled down off the cliff. This is due to uneven distribution of mass or a folded curved slip plane. Rockfall: fragments of rock break away from the cliff face, often due to freeze-thaw weathering Landslide: blocks of rock slide downhill
Mudflow: saturated soil and weak rock flows down a slope Rotational Slip: slump of saturated soil and weak rock along a curved surface Wave Types Constructive Waves: (Depositional) Surge up the beach with a powerful swash Carry large amounts of sediment and construct beach Formed by distant storms Waves well spaced apart and powerful when they reach the coast Destructive Waves: (Erosional) Weak swash and powerful backwash Scour the beach of material destroying beach Formed by local storms Closely spaced and can interfere with one another, producing chaotic, swirling mass of water Hydraulic Action (Power) Coastal Erosion Waves can erode the land by one of four processes
Waves trap air in cracks in the rock. The creates high pressure. Repeated compression widens cracks and breaks off rock Abrasion (Corrasion) Particles carried in the seawater scrape and rub against coastal rocks. This sandpaper effect removes small pieces from the coast. Corrosion (Solution) Seawater is a weak carbonic acid. If particles of alkaline rock e.g. chalk or limestone are carried in seawater they will eventually dissolve. Terminology Erosion the process by which rock or soil is gradually destroyed by wind, rain, or the sea Coastal Transportation
Traction: large pebbles are rolled along the seabed Saltation: a hopping or bouncing motion of particles too heavy to be suspended Suspension: particles are carried (suspended) within the water Solution: dissolved chemicals often derived from limestone or chalk Coastal Deposition Coastal Deposition takes place in areas where the flow of water slows down. Coasts are built up when the amount of deposition is greater than the amount of erosion Energy of the water is lost due to friction against the sea bed, meaning the sediment can no longer be carried or rolled along and has to be deposited. The amount of material deposited will increase when there is excessive erosion elsewhere on the coast, meaning that there is a lot of material to be deposited OR there is a lot of material transported into the area Landforms Caused by Erosion Headlands and Bays Cliffs rarely erode at an even pace. Where coastlines are made up of different rocks, rock that is particularly resistant to erosion erode
more slowly, forming headlands. Areas of weaker rock erode more quickly to form bays Cliffs and Wave Cut Platforms Waves cause most erosion at the foot of a cliff causing a wave-cut notch. This is enlarged as the erosion continues. This causes the rock above the notch to become unstable and eventually leads to cliff collapse. This process repeats over time, causing the cliff to retreat and leaves behind a wave cut platform Landforms Caused by Erosion Caves, Arches, Stacks and Stumps Headlands are usually made of resistant rock that have weaknesses such as cracks. Coastal Erosion at Holderness Reasons for Erosion Key Facts and Figures 1. Easily eroded rock: Boulder clay is likely to slump when wet, causing the cliffs to
collapse Holderness is in East Yorkshire and has one of the fastest eroding coastlines in Europe Flamborough Head (headland) is harder chalk The majority of the coastline is made of soft blouderclay Erosion rates (per year): Flamborough = 0.1m Average erosion = 1.8m Clay cliffs = 10m 2. Narrow beaches 3. People Beaches reduce energy of waves and therefore erosive power narrow beaches give less protection Coastal defences like groynes stop sediment moving down the coast,
meaning beaches are even narrower Helping You on Every Step of Your GCSE Geography Coastal Erosion at Holderness Impacts and Management Landforms Caused by Deposition 1. Sand Beaches Beaches are found between the high water mark (highest point on the land that the water will reach) and the low water mark. They are formed by constructive waves. There are 2 types of beach: Flat and Wide Sand particles are small Weak backwash able to move sand backwards to
create a long, gentle slope 2. Shingle Steep and narrow Shingle particles are large Weak backwash unable to move it back down beach Particles build up to create a steep slope Landforms Caused by Deposition Spits and Bars Spits are long, narrow finger shaped areas of sand or shingle that jut out into the sea. They are formed by longshore drift in areas where the coastline suddenly changes direction. They are attached to the coastline at one end. If it reaches out far enough to become attached to another piece of the mainland, it is called a bar. Explain why cliffs collapse. https://www.youtube.com/watch?v=TGxsC74H2Jw
Cliffs collapse due to a number of reasons These often occur in combination with one another. The power of the waves pounding against the base of the cliff between the HWM and LWM undercuts the cliffs and makes it unstable. The overhanging parts will eventually collapse. Heavy rainfall can add weight to the land and make it unstable, causing landslides or slumps to occur. This is especially likely if soft rock is present. Adding buildings to the cliff tops can have similar effects or even a lot of people walking on the cliff tops can have similar effects. People protecting the coast and interfering with longshore drift can prevent the movement of the sand to replenish beaches and expose the base of the cliffs to erosion. Discuss the costs and benefits of using hard engineering to reduce the risk of cliff collapse. How Can Coastlines be Managed? Hard Engineering Hard Engineering Approaches Hard Engineering involves using artificial structures to control the flow of the sea; reducing erosion and flooding. They are expensive and involve high maintenance costs Description Strategy SEA WALL
GROYNES ROCK ARMOUR Cost Concrete or rock barrier placed at top of beach or base of cliffs Recurved face to reflect waves back into sea Usually 3-5m high Upto 6 million per km Timber or rock built from coast out into sea Trap sediment moved by LSD to enlarge beach Beach acts as buffer to incoming waves, reducing
their energy and therefore erosion 10,000 each (every 200m) Piles of large boulders (resistant rock) at foot of cliff Rocks force waves to break, reducing energy and therefore erosion 1,000 to 4,000 per metre Advantages Disadvantages Effective at stopping sea
Often have walkways or promenade that people can walk upon Can act as a barrier to flooding Results in a bigger beach which can increase tourist potential Not too expensive Wider beach leads too added natural protection from flooding and further erosion Relatively cheap Often used by fishermen, so adds interest to the coast
Very expensive to create and maintain Can be unsightly Create a strong backwash, which will scour the beach or underneath the wall Problem is shifted rather than solved Starve beaches down drift of material, increasing erosion there; and increasing risk of flooding Unnatural looking, rock ones in particular are very unattractive Rocks are from elsewhere, which leads to expensive transport costs Can be moved during storms, so need to be replaced How Can Coastlines be Managed? Soft Engineering Soft Engineering Approaches Soft Engineering approaches try to fit in with the natural environment and coastal processes. They do not involve artificial structures. They are more environmentally and economically sustainable as they are unobtrusive and normally have low maintenance costs.
Description Strategy BEACH NOURISHMENT DUNE REGENERATION MARSH CREATION (MANAGED RETREAT) Cost Adding more sand or shingle to a beach to make it wider Sediment locally
sourced to blend in with existing beach Normally brought onshore by barge Appox. 3,000 per metre Sand dunes are effective barriers against the sea They are fragile, so easily destroyed Planting Marram Grass stabilises the dunes Fences will keep people off Approx. 2,000 per 100metres Involves allowing lowlying coastal areas to flood The area can become a salt marsh This provides a barrier to the sea
Dependant on value of land; arable land costs 5,000 to 10,000 per metre Advantages Disadvantages Relatively cheap and easy to maintain Blends in with existing beach Increases tourist potential due to larger beach Larger beach reduces risk of flooding and erosion Maintains a natural environment that attracts wildlife and tourists
Relatively cheap Cheap in comparison to implementing and maintaining sea defences Creates habitats for wildlife Flooding and erosion reduced behind the marshland Needs constant maintenance due to LSD moving material down drift Can kill organisms on sea bed
Time-consuming Relies on people responding to the fenced off areas Can be damaged by storms Protection is only limited to that area Land will be lost Farmers or landowners will need to be compensated Farmers livelihood would be affected COASTAL HABITAT Saltfleetby - Formation Key Facts and Figures Saltfleetby Theddlethorpe Dunes stretch 8km along the North Lincolnshire coastline Habitats include a saltmarsh and a variety of dunes It is a National Nature Reserve (NNR) and a Special Area for Conservation (SAC)
COASTAL HABITAT Saltfleetby Saltmarsh Characteristics Saltmarshes start as an accumulation of mud and silt in a sheltered part of the coastline Over time, more deposition allows the mud to break the surface and form mudflats. Salt-tolerant plants begin to colonise these are known as pioneer plants. As sediment is trapped by plants and they decay, the mud level begins to rise This reduces the salt content and increases fertility of the soil, allowing new species to grow - this is vegetation succession. COASTAL HABITAT Saltfleetby - Management Conservation and Sustainable use The area is conserved to preserve its natural habitat; but it still able to be used sustainably. The reserve is managed by Natural
England in partnership with the Lincolnshire Wildlife Trust and the Ministry of Defence. Coastal Management -New Forest Coastline Pressures on the Coastline The New Forest District Council is responsible for this stretch of coastline, and split it into 3 key areas Coastal Management -New Forest Coastline Management of the Coastline Coastal erosion needs to be managed, but the council need to decide whether it is worth protecting the area with sea defences, this is known as Cost-benefit analysis Rising Sea Levels - How Increases in the atmospheric concentrations of the greenhouse gases (carbon dioxide, methane, nitrous oxide and chlorofluorocarbons) is expected to result in substantial global-scale warming in the future. In response to this warming, global mean sea level will change, due to two main reasons. 2. Melting Ice Global warming is causing
Ice Caps (Ice covering land); glaciers and snow to melt. This water eventually runs to the sea, increasing the overall volume of water in the sea This is not the case for icebergs, as they displace the water, meaning there is no gain in water volume. 1. Thermal Expansion As oceans warm, its density decreases, which in turn increases the volume of water Rising Sea Levels - Maldives The Maldives are a maximum of 2.4m above sea level, putting them at great risk from sea level rise. There will be a variety of impacts Glossary Key Term Definition
Abrasion (Corrasion) Erosion caused by the rubbing and scouring effect of material carried by waves Attrition Erosion caused when rocks and boulders, transported by waves, bump into each other and break up into smaller pieces Backwash the movement of water down a beach to the sea Biological Weathering Weathering that involves the break down or degradation of rock by living organisms Chemical Weathering Weathering that involves a chemical change taking place Constructive Wave A powerful wave with a strong swash that surges up a beach
Corrosion (solution) Erosion caused by acids in waves dissolving rocks by chemical action Helping You on Every Step of Your GCSE Geography Glossary Key Term Definition Crest The top of a wave Destructive Wave A wave that crashes down onto a beach and has a powerful backwash Fetch distance wind has travelled over open water to create waves Freeze-thaw Weathering A process of physical weathering by which rock disintegrates due to water in cracks repeatedly freezing
and thawing Hard Engineering Building artificial structures such as sea walls aimed at controlling natural processes Hydraulic Power Erosion caused by the sheer force of water breaking off small pieces of rock Longshore Drift The movement of material along a coast by breaking waves Helping You on Every Step of Your GCSE Geography Glossary Key Term Definition Managed Retreat Allowing controlled flooding of low-lying coastal areas or cliff collapse in areas where the value of land is low Mass Movement
The downhill movement of weathered material under gravity Mechanical Weathering a process of weathering which results in smaller pieces of the same rock material being produced. Pioneer Plant a species or community of plant(s) that is first to colonise a previously barren area. Prevailing Wind The direction from which the wind usually blows Saltation A process of transportation in which small particles bounce along the bed in a leap-frog action Helping You on Every Step of Your GCSE Geography Glossary Key Term Definition
Soft Engineering A sustainable approach to managing the coast without using artificial structures Solution A process of transportation in which dissolved particles are carried in the water Suspension A process of transportation in which material is picked up and carried along with the water itself Swash the running of water up a beach under the momentum of a breaking wave Traction A process of transportation in which material is rolled along the bed Vegetation Succession A sequence of vegetation species colonising an
environment Weathering The breakdown of rocks by either mechanical processes or chemical changes Helping You on Every Step of Your GCSE Geography
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